Some 300 unmarked graves found two months ago in Thailand's restive south appear to hold bodies of slain migrant workers from neighbouring Cambodia and Myanmar, Thai authorities said Sunday.

Most of the bodies were found in late March in Pattani, one of three insurgency-hit provinces in southern Thailand. They were buried in unmarked graves at cemeteries for the region's ethnic Chinese community, the Central Institute of Forensic Science said.

About 30 bodies were found in Narathiwat province, and a few others in Yala.

"Police believe they were illegal immigrant workers from Cambodia and Myanmar, and 80 percent of them were killed," the center's deputy head Pornthip Rojanasunandtold AFP.

"We still don't yet know whether they were victims of the southern unrest."

But Pornthip said the finding has raised new concerns about human rights abuses in the region where 1,200 people have died in two years of unrest.

"Normally unidentified bodies must be well cared for, but Thailand lacks a system to treat them properly," she said.

The Thailand government has yet to approve funding to begin the process of identifying the bodies.

"Hopefully we can start to exhume the bodies and start to identify them. The process would take several months to complete," Pornthip said.

Most victims of the unrest in the Muslim-majority provinces along the southern border have been civilians.

The region was an independent sultanate until Thailand annexed it a century ago. Separatist violence has simmered ever since, with the latest insurgency erupting in January 2004.